Digital Voltage-Controlled Attenuator with Resistor Ladder
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Solution Overview
Problem
Current RF attenuators do not provide linear attenuation over a desired attenuation range, which is a limitation in wireless communication systems.
Innovation Solution
A digital voltage-controlled RF signal attenuator circuit is designed, comprising a balun and an attenuator with a resistor ladder and switches that adjust impedance based on a digital control signal, allowing for precise control of RF signal power through the opening and closing of switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If current RF attenuator implementations are used, then the device can provide signal attenuation, but the attenuation is not linear over the desired attenuation range
Solution Approach 1:
The attenuator is divided into multiple discrete resistance steps using a resistor ladder network with switches. Each switch corresponds to a specific attenuation level, allowing precise control over the attenuation amount. This segmentation enables linear attenuation control by selecting appropriate resistance values at each step, resolving the contradiction between attenuation linearity and adjustable range.
2Manufacturing precision
If the attenuator impedance is adjusted to control RF signal power, then linear attenuation over a broader range is achieved, but the device complexity increases
Solution Approach 1:
The attenuator uses dynamically controllable switches that can be programmed to different states based on desired attenuation levels. This dynamic control allows a single device to provide multiple attenuation levels, reducing the need for multiple fixed attenuators and simplifying the overall system architecture while maintaining precise linear control.
Solution Approach 2:
The attenuator changes its impedance parameter dynamically by switching between different resistance values in the ladder network. By controlling which switches are open or closed, the device can precisely adjust its impedance to achieve the desired attenuation level, providing linear control without requiring complex additional circuitry.
3Ease of operation
If digital switches are used to control attenuator impedance, then linear attenuation control is achieved, but insertion loss may increase
Solution Approach 1:
The resistor ladder network is designed with carefully selected resistance values that minimize insertion loss while maintaining linear attenuation control. By optimizing the resistance parameters at each ladder step, the device achieves good impedance matching across all attenuation levels, reducing reflections and minimizing energy loss despite the presence of digital switches.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables linear adjustment of RF signal power over a larger dynamic range, improving the attenuation control in wireless communication systems and reducing power consumption by varying the impedance of the attenuator.
Implementation Method 1
a balun configured to receive a radio frequency (RF) signal at a first input port and a second input port and configured to output the RF signal
Implementation Method 2
an attenuator coupled in parallel with the first and second input ports of the balun. A power level of the RF signal output by the balun is based at least partially on an impedance of the attenuator
Implementation Method 3
The plurality of switches are configured to open and close according to a digital control signal received by the switches such that the impedance of the attenuator, as experienced by the RF signal, is a function of which switches are open and which switches are closed
Data Source
AI summary
In accordance with some embodiments of the present disclosure an attenuating circuit comprises a balun configured to receive a radio frequency (RF) signal at first and second input ports and configured to output the RF signal. The circuit further comprises an attenuator coupled in parallel with the first and second input ports. A power level of the RF signal output by the balun is based at least partially on an impedance of the attenuator. The attenuator comprises a resistor ladder configured to receive at least a portion of the RF signal and a plurality of switches coupled to the resistor ladder. The plurality of switches are configured to open and close such that the impedance of the attenuator is a function of which switches are open and closed. Therefore, the power of the RF signal is controlled based at least on the opening and closing of the switches.